A rolling stand or apparatus for making seamless pipe typically has a massive stationary frame on which are mounted two driven tapered rolls with frustoconical outer surfaces and two Diescher disks. The rolls flank a normally vertical travel plane that bisects the horizontally moving workpiece, and the Diescher disks are above—and below the workpiece. The tapered rolls are rotatable about respective axes that form opposite but complementary small acute angles with the workpiece, and the Diescher disks rotate about axes perpendicular to the travel plane. The raw tubular workpiece is pressed against a piercing rod or mandrel by the four rotating tools to longitudinally stretch and radially compress it into an exactly dimensioned seamless pipe.
As described in U.S. Pat. No. 6,546,772, the roll stand is formed two portal frames lying spaced apart in the workpiece-travel direction and connected to each other by a lower traverse and an upper traverse. The upper transverse is slidable in guides between the portal frames to facilitate insertion and removal of the rolls.
Changing the rolls in the known double tapered-roll apparatus with an upper and a lower frustoconical roll is a time-consuming and difficult operation. First, the upper traverse must be moved horizontally to the side in order then to be able to lift the frustoconical rolls one after the other out of the roll stand with a crane. The surrounding equipment does not permit a movement of both stand sides or portal frames, so that simultaneous replacement of both rolls is not possible. Instead, this always takes place consecutively, never at the same time.